This invention provides an improved nonwoven primary carpet backing for use in preparing cut pile tufted carpets.
In the preparation of cut pile tufted carpets, the looper pulls the loop off of the needle during each stroke of the machine, thereby causing through abrasion an unwanted sharp edge and/or barb on the needle. The damaged needle thereafter tends to cut the primary carpet backing as the backing moves forward against the needle. This results in lower tufted tongue tear strength when nonwoven backings are employed.
Another problem with some nonwoven primary carpet backings is the tendency to develop fuzz. During beck dyeing of carpet, filaments tend to be pulled out of the nonwoven backing. Loose face yarn becomes tangled in these free filaments, forming unsightly balls of fiber on the edges and back of the carpets. These balls also create areas of poor delamination resistance in carpets when the usual secondary backing is applied.
Edwards, U.S. Pat. No. 3,563,838, teaches a method for preparing nonwoven polypropylene primary carpet backings with high tufted tongue tear strength and low neckdown in beck dyeing. This is accomplished through layering of the nonwoven material with filaments in one layer (the M layer) organized primarily in the machine direction, i.e., the general direction of belt travel, and filaments in an adjacent layer (the X layer) organized primarily in a direction across the width of the belt. The product of Edwards contains also a smaller proportion of filaments organized in the bias directions. The layered nonwoven webs of Edwards when bonded in saturated steam have high tufted tongue tear strength at a low level of neckdown. Edwards discloses sheets with both MX and MXM layer sequence.
U.S. Pat. No. 3,821,062 discloses a nonwoven polypropylene primary carpet backing which differs from the product in Edwards, U.S. Pat. No. 3,563,838, in a number of respects including binder content, matrix filament denier, tenacity and component distribution. This technology produces nonwoven MX sheets having a high level of unlatexed tear strength at a reasonable level of neckdown and which retain a high proportion of this tear resistance even after latexing.
Petersen, U.S. Pat. No. 3,502,538 discloses a nonwoven carpet backing which contains before bonding both amorphous polypropylene filaments and crystalline polypropylene filaments, the degree of crystallinity being controlled by the degree of drawing before deposit on the collecting belt. Petersen reports that a randomly-laid nonwoven carpet backing of mixed filament composition has less sensitivity to damaged (burred) needles than webs of single composition.
The present invention not only deals with the problem of damage caused by tufting with burred needles but is also concerned with fuzz resistance and high cover. In developing nonwoven carpet backings for use in cut pile carpets it has become apparent that this combination of properties is exceptionally difficult to obtain.